[Feature #20205]
As a path toward enabling frozen string literals by default in the future,
this commit introduce "chilled strings". From a user perspective chilled
strings pretend to be frozen, but on the first attempt to mutate them,
they lose their frozen status and emit a warning rather than to raise a
`FrozenError`.
Implementation wise, `rb_compile_option_struct.frozen_string_literal` is
no longer a boolean but a tri-state of `enabled/disabled/unset`.
When code is compiled with frozen string literals neither explictly enabled
or disabled, string literals are compiled with a new `putchilledstring`
instruction. This instruction is identical to `putstring` except it marks
the String with the `STR_CHILLED (FL_USER3)` and `FL_FREEZE` flags.
Chilled strings have the `FL_FREEZE` flag as to minimize the need to check
for chilled strings across the codebase, and to improve compatibility with
C extensions.
Notes:
- `String#freeze`: clears the chilled flag.
- `String#-@`: acts as if the string was mutable.
- `String#+@`: acts as if the string was mutable.
- `String#clone`: copies the chilled flag.
Co-authored-by: Jean Boussier <byroot@ruby-lang.org>
In preparation for https://bugs.ruby-lang.org/issues/20205.
The `frozen_string_literal` compilation option will no longer
be a boolean but a tri-state: `on/off/default`.
Using RSTRING_PTR can cause the string object to not exist on the stack,
which could cause it to be GC'd or be moved by GC compaction. This can
cause RSTRING_PTR to point to the incorrect location if the string is
embedded and moved by GC compaction.
Fixesruby/prism#2442.
assert does not print the bug report, only the file and line number of
the assertion that failed. RUBY_ASSERT prints the full bug report, which
makes it much easier to debug.
Before this commit, there were many places where we had to generate
dummy line nodes to hold both the line number and the node id that
would then immediately get pulled out from the created node. Now
we pass them explicitly so that we don't have to generate these
nodes.
This makes a clearer line between the parser and compiler, and also
makes it easier to generate instructions when we don't have a
specific node to tie them to. As such, it removes almost every
single place where we needed to previously generate dummy nodes.
This also makes it easier for the prism compiler, because now we
can pass in line number and node id instead of trying to generate
dummy nodes for every instruction that we compile.
